This invention relates generally to an imaging system for forming a plurality of images and, more specifically, to such a system which includes an electrooptic imaging member.
There is known in the imaging art a broad class of imaging devices which record optical images by an imagewise distribution of photogenerated voltages or currents acting upon a voltage or current-alterable recording medium. Examples of imaging devices which belong to this class are the Ruticon devices, FERPIC devices, Phototitus devices and liquid crystal devices. Typically, in these devices, imagewise activating radiation incident on a photoconductor allows charge carriers to move in an external electric field. These charge carriers interact with a voltage or current-sensitive member which, in turn, modulates light.
In the Ruticon (derived from the Greek words "rutis" for wrinkle and "icon" of image) family of devices described by Sheridon in IEEE Transactions on Electron Devices, September, 1972, and U.S. Pat. No. 3,716,359, the voltage-sensitive, light modulating recording medium comprises a deformable elastomer layer and the photoconductive material may be provided as a separate layer or incorporated in the elastomer layer. Various embodiments for establishing an electric field across the elastomer layer are possible including depositing a thin metallic conductive layer which serves as an electrode over the elastomer layer in the embodiment referred to as the .gamma.-Ruticon.
The Phototitus devices, described by Grenat, Pergrale, Donjon and Marie, Applied Physics Letters, Vol. 21, No. 3, Aug. 1, 1972, have sandwich structures comprising a KD.sub.2 PO.sub.4 crystal as the voltage-sensitive, light modulating layer arranged adjacent to a photoconductive layer. The KD.sub.2 PO.sub.4 crystal reacts to the light-induced voltage distribution produced by the photoconductive layer by changing the polarization of transmitted light, a phenomenon called the electro-optic effect or the Pockels effect.
The FERPIC devices, which are described, for example, by Meitzler and Maldonado in Electronics, Feb. 1, 1971, and by Smith and Land in Applied Physics Letters, Vol. 24, No. 4, Feb. 15, 1972, include a PLZT (lead-zirconate titanate doped with Lanthanum) ceramic material as the voltage-sensitive, light modulating element. Like the KD.sub.2 PO.sub.4 crystal in the Phototitus devices, the PLZT ceramic material responds to the altered electric field produced by the photoconductive layer by changing the polarization of transmitted light. In some PLZT devices, the effect used is an electric field-induced change in the degree to which transmitted light is scattered. Unlike the KD.sub.2 PO.sub.4 crystals, the effects produced in the PLZT ceramics do not disappear when the electric field is removed. Because of their similarities, the materials used in the Phototitus and FERPIC devices will be referred to herein as "electrooptic effect materials."
Many imaging devices in which liquid crystalline materials are used as the recording medium are known such as, for example, those described by Margerum et al, Applied Physics Letters, Vol. 19, No. 7, Oct. 1, 1971. In these devices, the light modulating liquid crystal layer may be either voltage or current alterable. For example, devices which include nematic liquid crystalline materials as the recording medium display voltage-sensitive light modulating properties when operated above a certain threshold voltage. Various nematogenic materials will also exhibit dynamic scattering when acted upon by an electric current.
Electrooptic imaging devices of this general type have been the subject of increasing attention recently because of the many applications in which they may be utilized and the excellent performance which they are capable of providing. Two important areas where devices of this type may be effectively utilized are image intensification and image storage. In relatively new and growing areas of technology such as electrooptic imaging systems, new imaging members, materials for use in the imaging members and the use of the imaging members in new modes continue to be discovered. The present application relates to a novel and advantageous imaging system for forming a plurality of images on the same surface.